This application generally concerns optical probes.
An optical-imaging catheter or endoscope's optical system is usually fragile and is therefore protected by a sheath. Astigmatism is created in the optical system by the cylindrical shape of the sheath. Astigmatism causes the foci of the beams of light in two orthogonal directions to converge at different distances with different beam sizes or to diverge in one direction while converging in another direction. This astigmatism reduces the image quality of the optical system.